21215587 has 2 divisors, whose sum is σ = 21215588. Its totient is φ = 21215586.

The previous prime is 21215569. The next prime is 21215599. The reversal of 21215587 is 78551212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21215587 - 2⁷ = 21215459 is a prime.

It is a super-2 number, since 2×21215587² = 900202263509138, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21215287) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10607793 + 10607794.

It is an arithmetic number, because the mean of its divisors is an integer number (10607794).

Almost surely, 2^21215587 is an apocalyptic number.

21215587 is a deficient number, since it is larger than the sum of its proper divisors (1).

21215587 is an equidigital number, since it uses as much as digits as its factorization.

21215587 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5600, while the sum is 31.

The square root of 21215587 is about 4606.0381023174. The cubic root of 21215587 is about 276.8333134181.

Adding to 21215587 its reverse (78551212), we get a palindrome (99766799).

The spelling of 21215587 in words is "twenty-one million, two hundred fifteen thousand, five hundred eighty-seven".